1 /* 2 * linux/kernel/fork.c 3 * 4 * Copyright (C) 1991, 1992 Linus Torvalds 5 */ 6 7 /* 8 * 'fork.c' contains the help-routines for the 'fork' system call 9 * (see also entry.S and others). 10 * Fork is rather simple, once you get the hang of it, but the memory 11 * management can be a bitch. See 'mm/memory.c': 'copy_page_range()' 12 */ 13 14 #include <linux/config.h> 15 #include <linux/slab.h> 16 #include <linux/init.h> 17 #include <linux/unistd.h> 18 #include <linux/smp_lock.h> 19 #include <linux/module.h> 20 #include <linux/vmalloc.h> 21 #include <linux/completion.h> 22 #include <linux/namespace.h> 23 #include <linux/personality.h> 24 #include <linux/mempolicy.h> 25 #include <linux/sem.h> 26 #include <linux/file.h> 27 #include <linux/key.h> 28 #include <linux/binfmts.h> 29 #include <linux/mman.h> 30 #include <linux/fs.h> 31 #include <linux/cpu.h> 32 #include <linux/cpuset.h> 33 #include <linux/security.h> 34 #include <linux/swap.h> 35 #include <linux/syscalls.h> 36 #include <linux/jiffies.h> 37 #include <linux/futex.h> 38 #include <linux/rcupdate.h> 39 #include <linux/ptrace.h> 40 #include <linux/mount.h> 41 #include <linux/audit.h> 42 #include <linux/profile.h> 43 #include <linux/rmap.h> 44 #include <linux/acct.h> 45 46 #include <asm/pgtable.h> 47 #include <asm/pgalloc.h> 48 #include <asm/uaccess.h> 49 #include <asm/mmu_context.h> 50 #include <asm/cacheflush.h> 51 #include <asm/tlbflush.h> 52 53 /* 54 * Protected counters by write_lock_irq(&tasklist_lock) 55 */ 56 unsigned long total_forks; /* Handle normal Linux uptimes. */ 57 int nr_threads; /* The idle threads do not count.. */ 58 59 int max_threads; /* tunable limit on nr_threads */ 60 61 DEFINE_PER_CPU(unsigned long, process_counts) = 0; 62 63 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */ 64 65 EXPORT_SYMBOL(tasklist_lock); 66 67 int nr_processes(void) 68 { 69 int cpu; 70 int total = 0; 71 72 for_each_online_cpu(cpu) 73 total += per_cpu(process_counts, cpu); 74 75 return total; 76 } 77 78 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 79 # define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL) 80 # define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk)) 81 static kmem_cache_t *task_struct_cachep; 82 #endif 83 84 /* SLAB cache for signal_struct structures (tsk->signal) */ 85 kmem_cache_t *signal_cachep; 86 87 /* SLAB cache for sighand_struct structures (tsk->sighand) */ 88 kmem_cache_t *sighand_cachep; 89 90 /* SLAB cache for files_struct structures (tsk->files) */ 91 kmem_cache_t *files_cachep; 92 93 /* SLAB cache for fs_struct structures (tsk->fs) */ 94 kmem_cache_t *fs_cachep; 95 96 /* SLAB cache for vm_area_struct structures */ 97 kmem_cache_t *vm_area_cachep; 98 99 /* SLAB cache for mm_struct structures (tsk->mm) */ 100 static kmem_cache_t *mm_cachep; 101 102 void free_task(struct task_struct *tsk) 103 { 104 free_thread_info(tsk->thread_info); 105 free_task_struct(tsk); 106 } 107 EXPORT_SYMBOL(free_task); 108 109 void __put_task_struct(struct task_struct *tsk) 110 { 111 WARN_ON(!(tsk->exit_state & (EXIT_DEAD | EXIT_ZOMBIE))); 112 WARN_ON(atomic_read(&tsk->usage)); 113 WARN_ON(tsk == current); 114 115 if (unlikely(tsk->audit_context)) 116 audit_free(tsk); 117 security_task_free(tsk); 118 free_uid(tsk->user); 119 put_group_info(tsk->group_info); 120 121 if (!profile_handoff_task(tsk)) 122 free_task(tsk); 123 } 124 125 void __init fork_init(unsigned long mempages) 126 { 127 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR 128 #ifndef ARCH_MIN_TASKALIGN 129 #define ARCH_MIN_TASKALIGN L1_CACHE_BYTES 130 #endif 131 /* create a slab on which task_structs can be allocated */ 132 task_struct_cachep = 133 kmem_cache_create("task_struct", sizeof(struct task_struct), 134 ARCH_MIN_TASKALIGN, SLAB_PANIC, NULL, NULL); 135 #endif 136 137 /* 138 * The default maximum number of threads is set to a safe 139 * value: the thread structures can take up at most half 140 * of memory. 141 */ 142 max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); 143 144 /* 145 * we need to allow at least 20 threads to boot a system 146 */ 147 if(max_threads < 20) 148 max_threads = 20; 149 150 init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; 151 init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; 152 init_task.signal->rlim[RLIMIT_SIGPENDING] = 153 init_task.signal->rlim[RLIMIT_NPROC]; 154 } 155 156 static struct task_struct *dup_task_struct(struct task_struct *orig) 157 { 158 struct task_struct *tsk; 159 struct thread_info *ti; 160 161 prepare_to_copy(orig); 162 163 tsk = alloc_task_struct(); 164 if (!tsk) 165 return NULL; 166 167 ti = alloc_thread_info(tsk); 168 if (!ti) { 169 free_task_struct(tsk); 170 return NULL; 171 } 172 173 *ti = *orig->thread_info; 174 *tsk = *orig; 175 tsk->thread_info = ti; 176 ti->task = tsk; 177 178 /* One for us, one for whoever does the "release_task()" (usually parent) */ 179 atomic_set(&tsk->usage,2); 180 atomic_set(&tsk->fs_excl, 0); 181 return tsk; 182 } 183 184 #ifdef CONFIG_MMU 185 static inline int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm) 186 { 187 struct vm_area_struct *mpnt, *tmp, **pprev; 188 struct rb_node **rb_link, *rb_parent; 189 int retval; 190 unsigned long charge; 191 struct mempolicy *pol; 192 193 down_write(&oldmm->mmap_sem); 194 flush_cache_mm(oldmm); 195 down_write(&mm->mmap_sem); 196 197 mm->locked_vm = 0; 198 mm->mmap = NULL; 199 mm->mmap_cache = NULL; 200 mm->free_area_cache = oldmm->mmap_base; 201 mm->cached_hole_size = ~0UL; 202 mm->map_count = 0; 203 cpus_clear(mm->cpu_vm_mask); 204 mm->mm_rb = RB_ROOT; 205 rb_link = &mm->mm_rb.rb_node; 206 rb_parent = NULL; 207 pprev = &mm->mmap; 208 209 for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) { 210 struct file *file; 211 212 if (mpnt->vm_flags & VM_DONTCOPY) { 213 long pages = vma_pages(mpnt); 214 mm->total_vm -= pages; 215 vm_stat_account(mm, mpnt->vm_flags, mpnt->vm_file, 216 -pages); 217 continue; 218 } 219 charge = 0; 220 if (mpnt->vm_flags & VM_ACCOUNT) { 221 unsigned int len = (mpnt->vm_end - mpnt->vm_start) >> PAGE_SHIFT; 222 if (security_vm_enough_memory(len)) 223 goto fail_nomem; 224 charge = len; 225 } 226 tmp = kmem_cache_alloc(vm_area_cachep, SLAB_KERNEL); 227 if (!tmp) 228 goto fail_nomem; 229 *tmp = *mpnt; 230 pol = mpol_copy(vma_policy(mpnt)); 231 retval = PTR_ERR(pol); 232 if (IS_ERR(pol)) 233 goto fail_nomem_policy; 234 vma_set_policy(tmp, pol); 235 tmp->vm_flags &= ~VM_LOCKED; 236 tmp->vm_mm = mm; 237 tmp->vm_next = NULL; 238 anon_vma_link(tmp); 239 file = tmp->vm_file; 240 if (file) { 241 struct inode *inode = file->f_dentry->d_inode; 242 get_file(file); 243 if (tmp->vm_flags & VM_DENYWRITE) 244 atomic_dec(&inode->i_writecount); 245 246 /* insert tmp into the share list, just after mpnt */ 247 spin_lock(&file->f_mapping->i_mmap_lock); 248 tmp->vm_truncate_count = mpnt->vm_truncate_count; 249 flush_dcache_mmap_lock(file->f_mapping); 250 vma_prio_tree_add(tmp, mpnt); 251 flush_dcache_mmap_unlock(file->f_mapping); 252 spin_unlock(&file->f_mapping->i_mmap_lock); 253 } 254 255 /* 256 * Link in the new vma and copy the page table entries. 257 */ 258 *pprev = tmp; 259 pprev = &tmp->vm_next; 260 261 __vma_link_rb(mm, tmp, rb_link, rb_parent); 262 rb_link = &tmp->vm_rb.rb_right; 263 rb_parent = &tmp->vm_rb; 264 265 mm->map_count++; 266 retval = copy_page_range(mm, oldmm, tmp); 267 268 if (tmp->vm_ops && tmp->vm_ops->open) 269 tmp->vm_ops->open(tmp); 270 271 if (retval) 272 goto out; 273 } 274 retval = 0; 275 out: 276 up_write(&mm->mmap_sem); 277 flush_tlb_mm(oldmm); 278 up_write(&oldmm->mmap_sem); 279 return retval; 280 fail_nomem_policy: 281 kmem_cache_free(vm_area_cachep, tmp); 282 fail_nomem: 283 retval = -ENOMEM; 284 vm_unacct_memory(charge); 285 goto out; 286 } 287 288 static inline int mm_alloc_pgd(struct mm_struct * mm) 289 { 290 mm->pgd = pgd_alloc(mm); 291 if (unlikely(!mm->pgd)) 292 return -ENOMEM; 293 return 0; 294 } 295 296 static inline void mm_free_pgd(struct mm_struct * mm) 297 { 298 pgd_free(mm->pgd); 299 } 300 #else 301 #define dup_mmap(mm, oldmm) (0) 302 #define mm_alloc_pgd(mm) (0) 303 #define mm_free_pgd(mm) 304 #endif /* CONFIG_MMU */ 305 306 __cacheline_aligned_in_smp DEFINE_SPINLOCK(mmlist_lock); 307 308 #define allocate_mm() (kmem_cache_alloc(mm_cachep, SLAB_KERNEL)) 309 #define free_mm(mm) (kmem_cache_free(mm_cachep, (mm))) 310 311 #include <linux/init_task.h> 312 313 static struct mm_struct * mm_init(struct mm_struct * mm) 314 { 315 atomic_set(&mm->mm_users, 1); 316 atomic_set(&mm->mm_count, 1); 317 init_rwsem(&mm->mmap_sem); 318 INIT_LIST_HEAD(&mm->mmlist); 319 mm->core_waiters = 0; 320 mm->nr_ptes = 0; 321 set_mm_counter(mm, file_rss, 0); 322 set_mm_counter(mm, anon_rss, 0); 323 spin_lock_init(&mm->page_table_lock); 324 rwlock_init(&mm->ioctx_list_lock); 325 mm->ioctx_list = NULL; 326 mm->default_kioctx = (struct kioctx)INIT_KIOCTX(mm->default_kioctx, *mm); 327 mm->free_area_cache = TASK_UNMAPPED_BASE; 328 mm->cached_hole_size = ~0UL; 329 330 if (likely(!mm_alloc_pgd(mm))) { 331 mm->def_flags = 0; 332 return mm; 333 } 334 free_mm(mm); 335 return NULL; 336 } 337 338 /* 339 * Allocate and initialize an mm_struct. 340 */ 341 struct mm_struct * mm_alloc(void) 342 { 343 struct mm_struct * mm; 344 345 mm = allocate_mm(); 346 if (mm) { 347 memset(mm, 0, sizeof(*mm)); 348 mm = mm_init(mm); 349 } 350 return mm; 351 } 352 353 /* 354 * Called when the last reference to the mm 355 * is dropped: either by a lazy thread or by 356 * mmput. Free the page directory and the mm. 357 */ 358 void fastcall __mmdrop(struct mm_struct *mm) 359 { 360 BUG_ON(mm == &init_mm); 361 mm_free_pgd(mm); 362 destroy_context(mm); 363 free_mm(mm); 364 } 365 366 /* 367 * Decrement the use count and release all resources for an mm. 368 */ 369 void mmput(struct mm_struct *mm) 370 { 371 if (atomic_dec_and_test(&mm->mm_users)) { 372 exit_aio(mm); 373 exit_mmap(mm); 374 if (!list_empty(&mm->mmlist)) { 375 spin_lock(&mmlist_lock); 376 list_del(&mm->mmlist); 377 spin_unlock(&mmlist_lock); 378 } 379 put_swap_token(mm); 380 mmdrop(mm); 381 } 382 } 383 EXPORT_SYMBOL_GPL(mmput); 384 385 /** 386 * get_task_mm - acquire a reference to the task's mm 387 * 388 * Returns %NULL if the task has no mm. Checks PF_BORROWED_MM (meaning 389 * this kernel workthread has transiently adopted a user mm with use_mm, 390 * to do its AIO) is not set and if so returns a reference to it, after 391 * bumping up the use count. User must release the mm via mmput() 392 * after use. Typically used by /proc and ptrace. 393 */ 394 struct mm_struct *get_task_mm(struct task_struct *task) 395 { 396 struct mm_struct *mm; 397 398 task_lock(task); 399 mm = task->mm; 400 if (mm) { 401 if (task->flags & PF_BORROWED_MM) 402 mm = NULL; 403 else 404 atomic_inc(&mm->mm_users); 405 } 406 task_unlock(task); 407 return mm; 408 } 409 EXPORT_SYMBOL_GPL(get_task_mm); 410 411 /* Please note the differences between mmput and mm_release. 412 * mmput is called whenever we stop holding onto a mm_struct, 413 * error success whatever. 414 * 415 * mm_release is called after a mm_struct has been removed 416 * from the current process. 417 * 418 * This difference is important for error handling, when we 419 * only half set up a mm_struct for a new process and need to restore 420 * the old one. Because we mmput the new mm_struct before 421 * restoring the old one. . . 422 * Eric Biederman 10 January 1998 423 */ 424 void mm_release(struct task_struct *tsk, struct mm_struct *mm) 425 { 426 struct completion *vfork_done = tsk->vfork_done; 427 428 /* Get rid of any cached register state */ 429 deactivate_mm(tsk, mm); 430 431 /* notify parent sleeping on vfork() */ 432 if (vfork_done) { 433 tsk->vfork_done = NULL; 434 complete(vfork_done); 435 } 436 if (tsk->clear_child_tid && atomic_read(&mm->mm_users) > 1) { 437 u32 __user * tidptr = tsk->clear_child_tid; 438 tsk->clear_child_tid = NULL; 439 440 /* 441 * We don't check the error code - if userspace has 442 * not set up a proper pointer then tough luck. 443 */ 444 put_user(0, tidptr); 445 sys_futex(tidptr, FUTEX_WAKE, 1, NULL, NULL, 0); 446 } 447 } 448 449 static int copy_mm(unsigned long clone_flags, struct task_struct * tsk) 450 { 451 struct mm_struct * mm, *oldmm; 452 int retval; 453 454 tsk->min_flt = tsk->maj_flt = 0; 455 tsk->nvcsw = tsk->nivcsw = 0; 456 457 tsk->mm = NULL; 458 tsk->active_mm = NULL; 459 460 /* 461 * Are we cloning a kernel thread? 462 * 463 * We need to steal a active VM for that.. 464 */ 465 oldmm = current->mm; 466 if (!oldmm) 467 return 0; 468 469 if (clone_flags & CLONE_VM) { 470 atomic_inc(&oldmm->mm_users); 471 mm = oldmm; 472 /* 473 * There are cases where the PTL is held to ensure no 474 * new threads start up in user mode using an mm, which 475 * allows optimizing out ipis; the tlb_gather_mmu code 476 * is an example. 477 */ 478 spin_unlock_wait(&oldmm->page_table_lock); 479 goto good_mm; 480 } 481 482 retval = -ENOMEM; 483 mm = allocate_mm(); 484 if (!mm) 485 goto fail_nomem; 486 487 /* Copy the current MM stuff.. */ 488 memcpy(mm, oldmm, sizeof(*mm)); 489 if (!mm_init(mm)) 490 goto fail_nomem; 491 492 if (init_new_context(tsk,mm)) 493 goto fail_nocontext; 494 495 retval = dup_mmap(mm, oldmm); 496 if (retval) 497 goto free_pt; 498 499 mm->hiwater_rss = get_mm_rss(mm); 500 mm->hiwater_vm = mm->total_vm; 501 502 good_mm: 503 tsk->mm = mm; 504 tsk->active_mm = mm; 505 return 0; 506 507 free_pt: 508 mmput(mm); 509 fail_nomem: 510 return retval; 511 512 fail_nocontext: 513 /* 514 * If init_new_context() failed, we cannot use mmput() to free the mm 515 * because it calls destroy_context() 516 */ 517 mm_free_pgd(mm); 518 free_mm(mm); 519 return retval; 520 } 521 522 static inline struct fs_struct *__copy_fs_struct(struct fs_struct *old) 523 { 524 struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); 525 /* We don't need to lock fs - think why ;-) */ 526 if (fs) { 527 atomic_set(&fs->count, 1); 528 rwlock_init(&fs->lock); 529 fs->umask = old->umask; 530 read_lock(&old->lock); 531 fs->rootmnt = mntget(old->rootmnt); 532 fs->root = dget(old->root); 533 fs->pwdmnt = mntget(old->pwdmnt); 534 fs->pwd = dget(old->pwd); 535 if (old->altroot) { 536 fs->altrootmnt = mntget(old->altrootmnt); 537 fs->altroot = dget(old->altroot); 538 } else { 539 fs->altrootmnt = NULL; 540 fs->altroot = NULL; 541 } 542 read_unlock(&old->lock); 543 } 544 return fs; 545 } 546 547 struct fs_struct *copy_fs_struct(struct fs_struct *old) 548 { 549 return __copy_fs_struct(old); 550 } 551 552 EXPORT_SYMBOL_GPL(copy_fs_struct); 553 554 static inline int copy_fs(unsigned long clone_flags, struct task_struct * tsk) 555 { 556 if (clone_flags & CLONE_FS) { 557 atomic_inc(¤t->fs->count); 558 return 0; 559 } 560 tsk->fs = __copy_fs_struct(current->fs); 561 if (!tsk->fs) 562 return -ENOMEM; 563 return 0; 564 } 565 566 static int count_open_files(struct fdtable *fdt) 567 { 568 int size = fdt->max_fdset; 569 int i; 570 571 /* Find the last open fd */ 572 for (i = size/(8*sizeof(long)); i > 0; ) { 573 if (fdt->open_fds->fds_bits[--i]) 574 break; 575 } 576 i = (i+1) * 8 * sizeof(long); 577 return i; 578 } 579 580 static struct files_struct *alloc_files(void) 581 { 582 struct files_struct *newf; 583 struct fdtable *fdt; 584 585 newf = kmem_cache_alloc(files_cachep, SLAB_KERNEL); 586 if (!newf) 587 goto out; 588 589 atomic_set(&newf->count, 1); 590 591 spin_lock_init(&newf->file_lock); 592 fdt = &newf->fdtab; 593 fdt->next_fd = 0; 594 fdt->max_fds = NR_OPEN_DEFAULT; 595 fdt->max_fdset = __FD_SETSIZE; 596 fdt->close_on_exec = &newf->close_on_exec_init; 597 fdt->open_fds = &newf->open_fds_init; 598 fdt->fd = &newf->fd_array[0]; 599 INIT_RCU_HEAD(&fdt->rcu); 600 fdt->free_files = NULL; 601 fdt->next = NULL; 602 rcu_assign_pointer(newf->fdt, fdt); 603 out: 604 return newf; 605 } 606 607 static int copy_files(unsigned long clone_flags, struct task_struct * tsk) 608 { 609 struct files_struct *oldf, *newf; 610 struct file **old_fds, **new_fds; 611 int open_files, size, i, error = 0, expand; 612 struct fdtable *old_fdt, *new_fdt; 613 614 /* 615 * A background process may not have any files ... 616 */ 617 oldf = current->files; 618 if (!oldf) 619 goto out; 620 621 if (clone_flags & CLONE_FILES) { 622 atomic_inc(&oldf->count); 623 goto out; 624 } 625 626 /* 627 * Note: we may be using current for both targets (See exec.c) 628 * This works because we cache current->files (old) as oldf. Don't 629 * break this. 630 */ 631 tsk->files = NULL; 632 error = -ENOMEM; 633 newf = alloc_files(); 634 if (!newf) 635 goto out; 636 637 spin_lock(&oldf->file_lock); 638 old_fdt = files_fdtable(oldf); 639 new_fdt = files_fdtable(newf); 640 size = old_fdt->max_fdset; 641 open_files = count_open_files(old_fdt); 642 expand = 0; 643 644 /* 645 * Check whether we need to allocate a larger fd array or fd set. 646 * Note: we're not a clone task, so the open count won't change. 647 */ 648 if (open_files > new_fdt->max_fdset) { 649 new_fdt->max_fdset = 0; 650 expand = 1; 651 } 652 if (open_files > new_fdt->max_fds) { 653 new_fdt->max_fds = 0; 654 expand = 1; 655 } 656 657 /* if the old fdset gets grown now, we'll only copy up to "size" fds */ 658 if (expand) { 659 spin_unlock(&oldf->file_lock); 660 spin_lock(&newf->file_lock); 661 error = expand_files(newf, open_files-1); 662 spin_unlock(&newf->file_lock); 663 if (error < 0) 664 goto out_release; 665 new_fdt = files_fdtable(newf); 666 /* 667 * Reacquire the oldf lock and a pointer to its fd table 668 * who knows it may have a new bigger fd table. We need 669 * the latest pointer. 670 */ 671 spin_lock(&oldf->file_lock); 672 old_fdt = files_fdtable(oldf); 673 } 674 675 old_fds = old_fdt->fd; 676 new_fds = new_fdt->fd; 677 678 memcpy(new_fdt->open_fds->fds_bits, old_fdt->open_fds->fds_bits, open_files/8); 679 memcpy(new_fdt->close_on_exec->fds_bits, old_fdt->close_on_exec->fds_bits, open_files/8); 680 681 for (i = open_files; i != 0; i--) { 682 struct file *f = *old_fds++; 683 if (f) { 684 get_file(f); 685 } else { 686 /* 687 * The fd may be claimed in the fd bitmap but not yet 688 * instantiated in the files array if a sibling thread 689 * is partway through open(). So make sure that this 690 * fd is available to the new process. 691 */ 692 FD_CLR(open_files - i, new_fdt->open_fds); 693 } 694 rcu_assign_pointer(*new_fds++, f); 695 } 696 spin_unlock(&oldf->file_lock); 697 698 /* compute the remainder to be cleared */ 699 size = (new_fdt->max_fds - open_files) * sizeof(struct file *); 700 701 /* This is long word aligned thus could use a optimized version */ 702 memset(new_fds, 0, size); 703 704 if (new_fdt->max_fdset > open_files) { 705 int left = (new_fdt->max_fdset-open_files)/8; 706 int start = open_files / (8 * sizeof(unsigned long)); 707 708 memset(&new_fdt->open_fds->fds_bits[start], 0, left); 709 memset(&new_fdt->close_on_exec->fds_bits[start], 0, left); 710 } 711 712 tsk->files = newf; 713 error = 0; 714 out: 715 return error; 716 717 out_release: 718 free_fdset (new_fdt->close_on_exec, new_fdt->max_fdset); 719 free_fdset (new_fdt->open_fds, new_fdt->max_fdset); 720 free_fd_array(new_fdt->fd, new_fdt->max_fds); 721 kmem_cache_free(files_cachep, newf); 722 goto out; 723 } 724 725 /* 726 * Helper to unshare the files of the current task. 727 * We don't want to expose copy_files internals to 728 * the exec layer of the kernel. 729 */ 730 731 int unshare_files(void) 732 { 733 struct files_struct *files = current->files; 734 int rc; 735 736 if(!files) 737 BUG(); 738 739 /* This can race but the race causes us to copy when we don't 740 need to and drop the copy */ 741 if(atomic_read(&files->count) == 1) 742 { 743 atomic_inc(&files->count); 744 return 0; 745 } 746 rc = copy_files(0, current); 747 if(rc) 748 current->files = files; 749 return rc; 750 } 751 752 EXPORT_SYMBOL(unshare_files); 753 754 static inline int copy_sighand(unsigned long clone_flags, struct task_struct * tsk) 755 { 756 struct sighand_struct *sig; 757 758 if (clone_flags & (CLONE_SIGHAND | CLONE_THREAD)) { 759 atomic_inc(¤t->sighand->count); 760 return 0; 761 } 762 sig = kmem_cache_alloc(sighand_cachep, GFP_KERNEL); 763 tsk->sighand = sig; 764 if (!sig) 765 return -ENOMEM; 766 spin_lock_init(&sig->siglock); 767 atomic_set(&sig->count, 1); 768 memcpy(sig->action, current->sighand->action, sizeof(sig->action)); 769 return 0; 770 } 771 772 static inline int copy_signal(unsigned long clone_flags, struct task_struct * tsk) 773 { 774 struct signal_struct *sig; 775 int ret; 776 777 if (clone_flags & CLONE_THREAD) { 778 atomic_inc(¤t->signal->count); 779 atomic_inc(¤t->signal->live); 780 return 0; 781 } 782 sig = kmem_cache_alloc(signal_cachep, GFP_KERNEL); 783 tsk->signal = sig; 784 if (!sig) 785 return -ENOMEM; 786 787 ret = copy_thread_group_keys(tsk); 788 if (ret < 0) { 789 kmem_cache_free(signal_cachep, sig); 790 return ret; 791 } 792 793 atomic_set(&sig->count, 1); 794 atomic_set(&sig->live, 1); 795 init_waitqueue_head(&sig->wait_chldexit); 796 sig->flags = 0; 797 sig->group_exit_code = 0; 798 sig->group_exit_task = NULL; 799 sig->group_stop_count = 0; 800 sig->curr_target = NULL; 801 init_sigpending(&sig->shared_pending); 802 INIT_LIST_HEAD(&sig->posix_timers); 803 804 sig->it_real_value = sig->it_real_incr = 0; 805 sig->real_timer.function = it_real_fn; 806 sig->real_timer.data = (unsigned long) tsk; 807 init_timer(&sig->real_timer); 808 809 sig->it_virt_expires = cputime_zero; 810 sig->it_virt_incr = cputime_zero; 811 sig->it_prof_expires = cputime_zero; 812 sig->it_prof_incr = cputime_zero; 813 814 sig->tty = current->signal->tty; 815 sig->pgrp = process_group(current); 816 sig->session = current->signal->session; 817 sig->leader = 0; /* session leadership doesn't inherit */ 818 sig->tty_old_pgrp = 0; 819 820 sig->utime = sig->stime = sig->cutime = sig->cstime = cputime_zero; 821 sig->nvcsw = sig->nivcsw = sig->cnvcsw = sig->cnivcsw = 0; 822 sig->min_flt = sig->maj_flt = sig->cmin_flt = sig->cmaj_flt = 0; 823 sig->sched_time = 0; 824 INIT_LIST_HEAD(&sig->cpu_timers[0]); 825 INIT_LIST_HEAD(&sig->cpu_timers[1]); 826 INIT_LIST_HEAD(&sig->cpu_timers[2]); 827 828 task_lock(current->group_leader); 829 memcpy(sig->rlim, current->signal->rlim, sizeof sig->rlim); 830 task_unlock(current->group_leader); 831 832 if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) { 833 /* 834 * New sole thread in the process gets an expiry time 835 * of the whole CPU time limit. 836 */ 837 tsk->it_prof_expires = 838 secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur); 839 } 840 841 return 0; 842 } 843 844 static inline void copy_flags(unsigned long clone_flags, struct task_struct *p) 845 { 846 unsigned long new_flags = p->flags; 847 848 new_flags &= ~(PF_SUPERPRIV | PF_NOFREEZE); 849 new_flags |= PF_FORKNOEXEC; 850 if (!(clone_flags & CLONE_PTRACE)) 851 p->ptrace = 0; 852 p->flags = new_flags; 853 } 854 855 asmlinkage long sys_set_tid_address(int __user *tidptr) 856 { 857 current->clear_child_tid = tidptr; 858 859 return current->pid; 860 } 861 862 /* 863 * This creates a new process as a copy of the old one, 864 * but does not actually start it yet. 865 * 866 * It copies the registers, and all the appropriate 867 * parts of the process environment (as per the clone 868 * flags). The actual kick-off is left to the caller. 869 */ 870 static task_t *copy_process(unsigned long clone_flags, 871 unsigned long stack_start, 872 struct pt_regs *regs, 873 unsigned long stack_size, 874 int __user *parent_tidptr, 875 int __user *child_tidptr, 876 int pid) 877 { 878 int retval; 879 struct task_struct *p = NULL; 880 881 if ((clone_flags & (CLONE_NEWNS|CLONE_FS)) == (CLONE_NEWNS|CLONE_FS)) 882 return ERR_PTR(-EINVAL); 883 884 /* 885 * Thread groups must share signals as well, and detached threads 886 * can only be started up within the thread group. 887 */ 888 if ((clone_flags & CLONE_THREAD) && !(clone_flags & CLONE_SIGHAND)) 889 return ERR_PTR(-EINVAL); 890 891 /* 892 * Shared signal handlers imply shared VM. By way of the above, 893 * thread groups also imply shared VM. Blocking this case allows 894 * for various simplifications in other code. 895 */ 896 if ((clone_flags & CLONE_SIGHAND) && !(clone_flags & CLONE_VM)) 897 return ERR_PTR(-EINVAL); 898 899 retval = security_task_create(clone_flags); 900 if (retval) 901 goto fork_out; 902 903 retval = -ENOMEM; 904 p = dup_task_struct(current); 905 if (!p) 906 goto fork_out; 907 908 retval = -EAGAIN; 909 if (atomic_read(&p->user->processes) >= 910 p->signal->rlim[RLIMIT_NPROC].rlim_cur) { 911 if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && 912 p->user != &root_user) 913 goto bad_fork_free; 914 } 915 916 atomic_inc(&p->user->__count); 917 atomic_inc(&p->user->processes); 918 get_group_info(p->group_info); 919 920 /* 921 * If multiple threads are within copy_process(), then this check 922 * triggers too late. This doesn't hurt, the check is only there 923 * to stop root fork bombs. 924 */ 925 if (nr_threads >= max_threads) 926 goto bad_fork_cleanup_count; 927 928 if (!try_module_get(p->thread_info->exec_domain->module)) 929 goto bad_fork_cleanup_count; 930 931 if (p->binfmt && !try_module_get(p->binfmt->module)) 932 goto bad_fork_cleanup_put_domain; 933 934 p->did_exec = 0; 935 copy_flags(clone_flags, p); 936 p->pid = pid; 937 retval = -EFAULT; 938 if (clone_flags & CLONE_PARENT_SETTID) 939 if (put_user(p->pid, parent_tidptr)) 940 goto bad_fork_cleanup; 941 942 p->proc_dentry = NULL; 943 944 INIT_LIST_HEAD(&p->children); 945 INIT_LIST_HEAD(&p->sibling); 946 p->vfork_done = NULL; 947 spin_lock_init(&p->alloc_lock); 948 spin_lock_init(&p->proc_lock); 949 950 clear_tsk_thread_flag(p, TIF_SIGPENDING); 951 init_sigpending(&p->pending); 952 953 p->utime = cputime_zero; 954 p->stime = cputime_zero; 955 p->sched_time = 0; 956 p->rchar = 0; /* I/O counter: bytes read */ 957 p->wchar = 0; /* I/O counter: bytes written */ 958 p->syscr = 0; /* I/O counter: read syscalls */ 959 p->syscw = 0; /* I/O counter: write syscalls */ 960 acct_clear_integrals(p); 961 962 p->it_virt_expires = cputime_zero; 963 p->it_prof_expires = cputime_zero; 964 p->it_sched_expires = 0; 965 INIT_LIST_HEAD(&p->cpu_timers[0]); 966 INIT_LIST_HEAD(&p->cpu_timers[1]); 967 INIT_LIST_HEAD(&p->cpu_timers[2]); 968 969 p->lock_depth = -1; /* -1 = no lock */ 970 do_posix_clock_monotonic_gettime(&p->start_time); 971 p->security = NULL; 972 p->io_context = NULL; 973 p->io_wait = NULL; 974 p->audit_context = NULL; 975 #ifdef CONFIG_NUMA 976 p->mempolicy = mpol_copy(p->mempolicy); 977 if (IS_ERR(p->mempolicy)) { 978 retval = PTR_ERR(p->mempolicy); 979 p->mempolicy = NULL; 980 goto bad_fork_cleanup; 981 } 982 #endif 983 984 p->tgid = p->pid; 985 if (clone_flags & CLONE_THREAD) 986 p->tgid = current->tgid; 987 988 if ((retval = security_task_alloc(p))) 989 goto bad_fork_cleanup_policy; 990 if ((retval = audit_alloc(p))) 991 goto bad_fork_cleanup_security; 992 /* copy all the process information */ 993 if ((retval = copy_semundo(clone_flags, p))) 994 goto bad_fork_cleanup_audit; 995 if ((retval = copy_files(clone_flags, p))) 996 goto bad_fork_cleanup_semundo; 997 if ((retval = copy_fs(clone_flags, p))) 998 goto bad_fork_cleanup_files; 999 if ((retval = copy_sighand(clone_flags, p))) 1000 goto bad_fork_cleanup_fs; 1001 if ((retval = copy_signal(clone_flags, p))) 1002 goto bad_fork_cleanup_sighand; 1003 if ((retval = copy_mm(clone_flags, p))) 1004 goto bad_fork_cleanup_signal; 1005 if ((retval = copy_keys(clone_flags, p))) 1006 goto bad_fork_cleanup_mm; 1007 if ((retval = copy_namespace(clone_flags, p))) 1008 goto bad_fork_cleanup_keys; 1009 retval = copy_thread(0, clone_flags, stack_start, stack_size, p, regs); 1010 if (retval) 1011 goto bad_fork_cleanup_namespace; 1012 1013 p->set_child_tid = (clone_flags & CLONE_CHILD_SETTID) ? child_tidptr : NULL; 1014 /* 1015 * Clear TID on mm_release()? 1016 */ 1017 p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL; 1018 1019 /* 1020 * Syscall tracing should be turned off in the child regardless 1021 * of CLONE_PTRACE. 1022 */ 1023 clear_tsk_thread_flag(p, TIF_SYSCALL_TRACE); 1024 #ifdef TIF_SYSCALL_EMU 1025 clear_tsk_thread_flag(p, TIF_SYSCALL_EMU); 1026 #endif 1027 1028 /* Our parent execution domain becomes current domain 1029 These must match for thread signalling to apply */ 1030 1031 p->parent_exec_id = p->self_exec_id; 1032 1033 /* ok, now we should be set up.. */ 1034 p->exit_signal = (clone_flags & CLONE_THREAD) ? -1 : (clone_flags & CSIGNAL); 1035 p->pdeath_signal = 0; 1036 p->exit_state = 0; 1037 1038 /* 1039 * Ok, make it visible to the rest of the system. 1040 * We dont wake it up yet. 1041 */ 1042 p->group_leader = p; 1043 INIT_LIST_HEAD(&p->ptrace_children); 1044 INIT_LIST_HEAD(&p->ptrace_list); 1045 1046 /* Perform scheduler related setup. Assign this task to a CPU. */ 1047 sched_fork(p, clone_flags); 1048 1049 /* Need tasklist lock for parent etc handling! */ 1050 write_lock_irq(&tasklist_lock); 1051 1052 /* 1053 * The task hasn't been attached yet, so its cpus_allowed mask will 1054 * not be changed, nor will its assigned CPU. 1055 * 1056 * The cpus_allowed mask of the parent may have changed after it was 1057 * copied first time - so re-copy it here, then check the child's CPU 1058 * to ensure it is on a valid CPU (and if not, just force it back to 1059 * parent's CPU). This avoids alot of nasty races. 1060 */ 1061 p->cpus_allowed = current->cpus_allowed; 1062 if (unlikely(!cpu_isset(task_cpu(p), p->cpus_allowed) || 1063 !cpu_online(task_cpu(p)))) 1064 set_task_cpu(p, smp_processor_id()); 1065 1066 /* 1067 * Check for pending SIGKILL! The new thread should not be allowed 1068 * to slip out of an OOM kill. (or normal SIGKILL.) 1069 */ 1070 if (sigismember(¤t->pending.signal, SIGKILL)) { 1071 write_unlock_irq(&tasklist_lock); 1072 retval = -EINTR; 1073 goto bad_fork_cleanup_namespace; 1074 } 1075 1076 /* CLONE_PARENT re-uses the old parent */ 1077 if (clone_flags & (CLONE_PARENT|CLONE_THREAD)) 1078 p->real_parent = current->real_parent; 1079 else 1080 p->real_parent = current; 1081 p->parent = p->real_parent; 1082 1083 if (clone_flags & CLONE_THREAD) { 1084 spin_lock(¤t->sighand->siglock); 1085 /* 1086 * Important: if an exit-all has been started then 1087 * do not create this new thread - the whole thread 1088 * group is supposed to exit anyway. 1089 */ 1090 if (current->signal->flags & SIGNAL_GROUP_EXIT) { 1091 spin_unlock(¤t->sighand->siglock); 1092 write_unlock_irq(&tasklist_lock); 1093 retval = -EAGAIN; 1094 goto bad_fork_cleanup_namespace; 1095 } 1096 p->group_leader = current->group_leader; 1097 1098 if (current->signal->group_stop_count > 0) { 1099 /* 1100 * There is an all-stop in progress for the group. 1101 * We ourselves will stop as soon as we check signals. 1102 * Make the new thread part of that group stop too. 1103 */ 1104 current->signal->group_stop_count++; 1105 set_tsk_thread_flag(p, TIF_SIGPENDING); 1106 } 1107 1108 if (!cputime_eq(current->signal->it_virt_expires, 1109 cputime_zero) || 1110 !cputime_eq(current->signal->it_prof_expires, 1111 cputime_zero) || 1112 current->signal->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY || 1113 !list_empty(¤t->signal->cpu_timers[0]) || 1114 !list_empty(¤t->signal->cpu_timers[1]) || 1115 !list_empty(¤t->signal->cpu_timers[2])) { 1116 /* 1117 * Have child wake up on its first tick to check 1118 * for process CPU timers. 1119 */ 1120 p->it_prof_expires = jiffies_to_cputime(1); 1121 } 1122 1123 spin_unlock(¤t->sighand->siglock); 1124 } 1125 1126 /* 1127 * inherit ioprio 1128 */ 1129 p->ioprio = current->ioprio; 1130 1131 SET_LINKS(p); 1132 if (unlikely(p->ptrace & PT_PTRACED)) 1133 __ptrace_link(p, current->parent); 1134 1135 cpuset_fork(p); 1136 1137 attach_pid(p, PIDTYPE_PID, p->pid); 1138 attach_pid(p, PIDTYPE_TGID, p->tgid); 1139 if (thread_group_leader(p)) { 1140 attach_pid(p, PIDTYPE_PGID, process_group(p)); 1141 attach_pid(p, PIDTYPE_SID, p->signal->session); 1142 if (p->pid) 1143 __get_cpu_var(process_counts)++; 1144 } 1145 1146 if (!current->signal->tty && p->signal->tty) 1147 p->signal->tty = NULL; 1148 1149 nr_threads++; 1150 total_forks++; 1151 write_unlock_irq(&tasklist_lock); 1152 retval = 0; 1153 1154 fork_out: 1155 if (retval) 1156 return ERR_PTR(retval); 1157 return p; 1158 1159 bad_fork_cleanup_namespace: 1160 exit_namespace(p); 1161 bad_fork_cleanup_keys: 1162 exit_keys(p); 1163 bad_fork_cleanup_mm: 1164 if (p->mm) 1165 mmput(p->mm); 1166 bad_fork_cleanup_signal: 1167 exit_signal(p); 1168 bad_fork_cleanup_sighand: 1169 exit_sighand(p); 1170 bad_fork_cleanup_fs: 1171 exit_fs(p); /* blocking */ 1172 bad_fork_cleanup_files: 1173 exit_files(p); /* blocking */ 1174 bad_fork_cleanup_semundo: 1175 exit_sem(p); 1176 bad_fork_cleanup_audit: 1177 audit_free(p); 1178 bad_fork_cleanup_security: 1179 security_task_free(p); 1180 bad_fork_cleanup_policy: 1181 #ifdef CONFIG_NUMA 1182 mpol_free(p->mempolicy); 1183 #endif 1184 bad_fork_cleanup: 1185 if (p->binfmt) 1186 module_put(p->binfmt->module); 1187 bad_fork_cleanup_put_domain: 1188 module_put(p->thread_info->exec_domain->module); 1189 bad_fork_cleanup_count: 1190 put_group_info(p->group_info); 1191 atomic_dec(&p->user->processes); 1192 free_uid(p->user); 1193 bad_fork_free: 1194 free_task(p); 1195 goto fork_out; 1196 } 1197 1198 struct pt_regs * __devinit __attribute__((weak)) idle_regs(struct pt_regs *regs) 1199 { 1200 memset(regs, 0, sizeof(struct pt_regs)); 1201 return regs; 1202 } 1203 1204 task_t * __devinit fork_idle(int cpu) 1205 { 1206 task_t *task; 1207 struct pt_regs regs; 1208 1209 task = copy_process(CLONE_VM, 0, idle_regs(®s), 0, NULL, NULL, 0); 1210 if (!task) 1211 return ERR_PTR(-ENOMEM); 1212 init_idle(task, cpu); 1213 unhash_process(task); 1214 return task; 1215 } 1216 1217 static inline int fork_traceflag (unsigned clone_flags) 1218 { 1219 if (clone_flags & CLONE_UNTRACED) 1220 return 0; 1221 else if (clone_flags & CLONE_VFORK) { 1222 if (current->ptrace & PT_TRACE_VFORK) 1223 return PTRACE_EVENT_VFORK; 1224 } else if ((clone_flags & CSIGNAL) != SIGCHLD) { 1225 if (current->ptrace & PT_TRACE_CLONE) 1226 return PTRACE_EVENT_CLONE; 1227 } else if (current->ptrace & PT_TRACE_FORK) 1228 return PTRACE_EVENT_FORK; 1229 1230 return 0; 1231 } 1232 1233 /* 1234 * Ok, this is the main fork-routine. 1235 * 1236 * It copies the process, and if successful kick-starts 1237 * it and waits for it to finish using the VM if required. 1238 */ 1239 long do_fork(unsigned long clone_flags, 1240 unsigned long stack_start, 1241 struct pt_regs *regs, 1242 unsigned long stack_size, 1243 int __user *parent_tidptr, 1244 int __user *child_tidptr) 1245 { 1246 struct task_struct *p; 1247 int trace = 0; 1248 long pid = alloc_pidmap(); 1249 1250 if (pid < 0) 1251 return -EAGAIN; 1252 if (unlikely(current->ptrace)) { 1253 trace = fork_traceflag (clone_flags); 1254 if (trace) 1255 clone_flags |= CLONE_PTRACE; 1256 } 1257 1258 p = copy_process(clone_flags, stack_start, regs, stack_size, parent_tidptr, child_tidptr, pid); 1259 /* 1260 * Do this prior waking up the new thread - the thread pointer 1261 * might get invalid after that point, if the thread exits quickly. 1262 */ 1263 if (!IS_ERR(p)) { 1264 struct completion vfork; 1265 1266 if (clone_flags & CLONE_VFORK) { 1267 p->vfork_done = &vfork; 1268 init_completion(&vfork); 1269 } 1270 1271 if ((p->ptrace & PT_PTRACED) || (clone_flags & CLONE_STOPPED)) { 1272 /* 1273 * We'll start up with an immediate SIGSTOP. 1274 */ 1275 sigaddset(&p->pending.signal, SIGSTOP); 1276 set_tsk_thread_flag(p, TIF_SIGPENDING); 1277 } 1278 1279 if (!(clone_flags & CLONE_STOPPED)) 1280 wake_up_new_task(p, clone_flags); 1281 else 1282 p->state = TASK_STOPPED; 1283 1284 if (unlikely (trace)) { 1285 current->ptrace_message = pid; 1286 ptrace_notify ((trace << 8) | SIGTRAP); 1287 } 1288 1289 if (clone_flags & CLONE_VFORK) { 1290 wait_for_completion(&vfork); 1291 if (unlikely (current->ptrace & PT_TRACE_VFORK_DONE)) 1292 ptrace_notify ((PTRACE_EVENT_VFORK_DONE << 8) | SIGTRAP); 1293 } 1294 } else { 1295 free_pidmap(pid); 1296 pid = PTR_ERR(p); 1297 } 1298 return pid; 1299 } 1300 1301 void __init proc_caches_init(void) 1302 { 1303 sighand_cachep = kmem_cache_create("sighand_cache", 1304 sizeof(struct sighand_struct), 0, 1305 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1306 signal_cachep = kmem_cache_create("signal_cache", 1307 sizeof(struct signal_struct), 0, 1308 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1309 files_cachep = kmem_cache_create("files_cache", 1310 sizeof(struct files_struct), 0, 1311 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1312 fs_cachep = kmem_cache_create("fs_cache", 1313 sizeof(struct fs_struct), 0, 1314 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1315 vm_area_cachep = kmem_cache_create("vm_area_struct", 1316 sizeof(struct vm_area_struct), 0, 1317 SLAB_PANIC, NULL, NULL); 1318 mm_cachep = kmem_cache_create("mm_struct", 1319 sizeof(struct mm_struct), 0, 1320 SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL, NULL); 1321 } 1322